REFRIGERATION AND FREEZING OF FISH 



343 



a dip for fillets in order to prevent drip after thawing. The alkaline dip modified 

 the pH of the fish tissues so as to increase their water-holding capacity. Alkaline 

 dips are not commonly used, but nitrites are used by many Canadian fish packers 



Fig. 16-6. Conveyor removing fillets from brining machine. Brining 

 fillets reduces the amount of drip or leakage which appears when the 

 frozen product is thawed. 



to lighten the color of the fillets. Nitrites also possess antiseptic properties. Conse- 

 quently, fillets dipped in nitrite solutions will not spoil quickly because of bacterial 

 growth. 



Packaging Fresh Fillets. The brined fillets drain as they are conveyed to cor- 

 rosion-resistant pans, in which they are carried to packing tables. 



Many different types of packages and wrappers are used for fillets. Iced fillets, 

 marketed without freezing, are commonly individually wrapped in vegetable 

 parchment paper and then packed in rectangular 30-pound japanned or tinned 

 metal fillet cans, having slipcovers. Some fresh fillets are packed in 5-, 10- or 

 20-pound waxed paperboard or fiberboard cartons, usually fitted with telescoping 

 covers. 



Chilled fillets of very high quality are produced by quickly coohng the packages 

 with rapidly moving air at about 0°F (— 18°C) in an air-blast tunnel. The fillets 

 are kept in the tunnel until ice crystals begin to form, at which point the 

 temperature of the fillets has been reduced to 28 to 30° F ( - 2.2 to - 1.1° C). 

 The containers of fillets are then packed in fiberboard boxes and rushed to market. 

 Fillets which have been quickly chilled in this manner and then shipped by air 



